Steve Naranjo, Ph.D. (left), and colleague Peter Ellsworth, Ph.D., sample sweetpotato whiteflies (Bemisia tabaci), also sometimes known as silverleaf whiteflies, in a cotton field. Naranjo and his sister were the first in their extended family to graduate from college. He went on to earn a master’s and doctorate in entomology, and he eventually become director of the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) Arid Land Agricultural Research Center in Maricopa, Arizona. Naranjo says, “My father cried when I told him I had become the center director. It was pretty touching.” He actively encourages Hispanic students and others in underrepresented groups to likewise pursue entomology and science as a highly rewarding career. (Photo credit: USDA-ARS)

By Leslie Mertz, Ph.D.

Leslie Mertz, Ph.D.

Editor’s Note: The Entomological Society of America is honoring the work of Hispanic and Latin American scientists in entomology during National Hispanic Heritage Month, September 15 to October 15. Below, Entomology Today highlights the career of new ESA Honorary Member Steve Naranjo, Ph.D. ESA also encourages members to mark their calendars for the 9th Latin American/Hispanic Symposium: Rising Strong in Entomology at Entomology 2021, taking place in-person and online, October 31 – November 3, in Denver, Colorado. Follow along here at Entomology Today and on Twitter for additional stories and features during Hispanic Heritage Month.

Cotton farming in Arizona has changed over the past 25 years. Today, pesticide use has decreased dramatically, while beneficial insect populations and biodiversity overall are gaining strength. Much of the reason can be traced to entomologist Steve Naranjo, Ph.D., who co-led a multi-pronged effort over several years to diversify cotton growers’ pest management approaches. New methods he and colleagues introduced included exchanging broad-spectrum pesticides for those that are much more selective for pest species, encouraging natural enemies to suppress pest populations, and planting transgenic cotton varieties that are selectively toxic to pests.

Steve Naranjo, Ph.D.

“I’ve been very fortunate to have a really good colleague in Peter Ellsworth [an entomologist at the University of Arizona], and together I think we can take a fair amount of credit for transforming Arizona cotton growing from being a very intensive, insecticide-based system to one that is selective- and biological-control based,” says Naranjo. Since 1996, he adds, Arizona growers have saved more than $500 million by using this multipronged, integrated pest management (IPM) approach. “And we’ve estimated that about $240 million of that total has been directly from the benefit of biological control, so that’s been a very positive thing.”

In addition to his work on IPM for cotton growers, Naranjo serves as director of the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS) Arid Land Agricultural Research Center in Maricopa, Arizona, and oversees an active multi-disciplinary research program, which has a vigorous intern program that focuses on students who are Hispanic, like himself, or members of other underrepresented groups. Of the program, he says, “I feel it’s important to give kids opportunities because I benefited so much from numerous opportunities when I was coming up.”

In September, Naranjo was selected an Honorary Member of the Entomological Society of America, in recognition of his long-term dedication and significant contributions to the Society.

Starting Out

Like many youngsters, Naranjo spent many a joy-filled hour chasing butterflies and moths, but he didn’t think about entomology as a career until he was well into the zoology undergraduate program at Colorado State University. “In the first semester of my senior year, I took an entomology class, which was one of those courses I needed to fill in my zoology curriculum, and we had to do a collection. And, wow, that just hooked me, because I started to appreciate that there all kinds of things beyond butterflies and moths out there,” he says.

Then, in the next semester, he got the chance to do a work study with an up-and-coming entomologist named John Capinera, Ph.D., who would eventually become the longtime chair of the University of Florida Department of Entomology and Nematology. “He really put me on the track toward doing this as a profession, in part by letting me have a lot of freedom to explore and even to publish three papers as an undergraduate student. That was really wonderful,” Naranjo says. After earning his bachelor’s degree, he continued his education and earned both a master’s and doctorate in entomology.

While doing his graduate work, Naranjo became interested in applied entomology, because it combined his interest in insect biology and ecology with his other passions for problem solving and making a difference, he says. “I could see the prospects within pest management in particular, so that’s the direction my program went.”

The IPM Effort

After finishing his doctorate in 1987, Naranjo began work for the USDA-ARS, and by 1990 he turned his attention toward IPM for cotton growers in Arizona, where he was then stationed. At that time, a major cotton pest called sweetpotato whitefly (Bemisia tabaci), also sometimes known as silverleaf whitefly, had arrived in the state and was quickly becoming resistant to all available broad-spectrum insecticides. Naranjo and Ellsworth teamed up to investigate new and reportedly selective and highly effective pesticides that were under study by researchers in other parts of the world. Ellsworth was instrumental in obtaining an emergency registration for the materials, and together they conducted their own research to verify that they were as good as claimed. They also developed strategies for using them to greatest advantage.

The growers took the recommendations to heart, and almost immediately Naranjo and Ellsworth saw overall pesticide use drop by two-thirds, from 10-12 applications per season to three or four.

Pesticide-resistant sweetpotato whiteflies (Bemisia tabaci), also sometimes known as silverleaf whiteflies, in Arizona cotton fields spurred Steve Naranjo, Ph.D., and colleague Peter Ellsworth, Ph.D., to study and obtain an emergency registration for new selective pesticides and develop strategies for using them to greatest advantage. A pair of the whiteflies are shown here feeding on a watermelon leaf. (Photo by Stephen Ausmus, USDA-ARS)

Besides reducing the frequency of sprays, which saves growers money, the switch to selective pesticides allows other insects to survive and thrive. That not only fosters overall biodiversity in the cotton fields, Naranjo says, but it also increases the populations of natural enemies of the pests, which can decrease the need for pesticides even further.

On top of that, transgenic Bt cotton became available to battle another major cotton pest called pink bollworm (Pectinophora gossypiella). Bt cotton is genetically engineered to produce pest-killing proteins made by the bacterium Bacillus thuringiensis. Although he wasn’t involved in the development of Bt cotton, Naranjo conducted exhaustive studies of the non-target impacts of Bt cotton to make sure it was safe to use and also participated in a global review of broader Bt crops, such as corn, eggplant, and rice. “There will always be detractors of the technology out there, but the more we learn, the more we see how selective and beneficial this technology is,” Naranjo says.

With this IPM approach, Arizona cotton growers today spray just one or two times a season. “We aren’t the only ones doing this kind IPM work, but our specific circumstance has certainly had tremendous success,” he says. “It’s been very satisfying to be a part of that.”

A Good Fit

The USDA-ARS has been an excellent fit throughout Naranjo’s career because it encourages applied research that solves problems and makes a difference, he says. “And what’s really nice about ARS is that we’re often either co-located or even integrated into university environments,” he says, “so in some cases you can walk down a hall in a university building, and the office on the left is a university person and the office on the right is an ARS person.”

In fact, Naranjo holds an adjunct position at the University of Arizona. “It really is the best of both worlds: you can have your job with USDA, which provides a certain amount of background funding to get your work done, and you can still interact with and mentor students.” He has co-advised several master’s and Ph.D. students and is currently working with a Brazilian Ph.D. student at the University of Arizona to finish up her research project. “It’s been very rewarding working with graduate students, because you feel like you really do get to give back at a higher level,” he says.

The USDA-ARS hasn’t been a good fit just for him. Naranjo believes the agency—and others in the federal government—are excellent places for any student to consider starting a career. “When I speak to groups of students, such as an Arizona State University group that mentors women in the sciences, I just love to be able to tell them about the opportunities in the federal government, and not just ARS but the U.S. Forest Service, the USDA’s Animal and Plant Health Inspection Service, the Environmental Protection Agency, and lots of other science agencies.”

He adds, “I’ve been very fortunate at the USDA-ARS, and, honestly, I couldn’t write a better script for how my career has gone: I wanted to have an impact and make a difference, and I’ve been very lucky that it’s turned out that way.”

Leslie Mertz, Ph.D., writes about science and runs an educational insect-identification website, www.knowyourinsects.org. She resides in northern Michigan.